1. Field of the Invention
The present invention relates to a TFT liquid crystal display constituting an active-matrix-type display device, and more particularly to a display device which can realize a display with little degradation of image quality with low power consumption and at a low cost.
2. Description of the Related Art
Currently, a TFT liquid crystal display (hereinafter, referred to as “LCD/”) which constitutes an active-matrix-type display device has been popularly used as a display device of a personal digital assistant including a mobile phone due to characteristics thereof such as small thickness, high definition and low power consumption. In the LCD, by controlling turning on/off of thin film transistors (hereinafter, referred to as “TFT”) mounted on respective liquid crystal pixels arranged in a matrix array in the horizontal as well as vertical direction in response to a gate voltage outputted from a gate driver, a data voltage outputted from a data driver is applied to liquid crystal thus controlling a transmissive/non-transmissive state of liquid crystal based on a potential difference between a common-line potential (Vcom) and the data voltage.
With respect to the characteristic of the liquid crystal, it has been known that the driving of the liquid crystal requires AC driving which inverts the polarity (potential level) of an applied voltage from the first polarity (positive polarity having a potential higher than the common-line potential (Vcom)) to the second polarity (negative polarity having a potential lower than the common-line potential (Vcom)) and from the second polarity to the first polarity at certain intervals.
As the AC driving of the liquid crystal in the LCD for the personal digital assistant, in general, the frame inversion driving which allows all liquid crystal pixels to have the same polarity and inverts the polarity of all liquid crystal pixels for every frame, and the line inversion driving which allows all liquid crystal pixels to have the same polarity in the horizontal direction, allows the polarity of the liquid crystal pixels to be inverted for every N lines in the vertical direction, and inverts the polarity of all liquid crystal pixels for every frame are used.
Further, the LCD for the personal data assistant adopts, in general, a driving method which reduces the power consumption by suppressing amplitude of a data line potential by combining the common inversion driving which simultaneously inverts the polarity of the common-line potential in addition to the inversion of the polarity of the data line potential with the above-mentioned driving. However, in the frame inversion driving and the line inversion driving, a considerable smear (a phenomenon which generates stripes in the horizontal as well as vertical direction) or considerable flickering (a phenomenon in which a screen flickers) is generated in the LCD thus degrading image quality.
To acquire a display with little degradation of image quality, AC driving of the liquid crystal by dot inversion driving which inverts the polarity for every liquid crystal pixel in both of horizontal and vertical directions, and also inverts the polarity of all liquid crystal pixels for every frame is effective. However, the dot inversion driving gives rise to new drawbacks such as a high withstand voltage of a driver LSI for driving the LCD or the increase of power consumption. On the other hand, particularly, with respect to a mobile phone, along with the increase of the number of users who make use of functions such as the reproduction of recorded motion images and a perusal of a Website using the mobile phone, there has been a demand for higher resolution of the LCD which can display large quantity of information at a time with high quality and hence, the realization of dot inversion driving with low power consumption and at a low cost is desired.
To cope with drawbacks which arise due to the above-mentioned dot inversion driving, particularly, to cope with the drawback in the power consumption, US Laid-open Patent 2006/0125986 (JP-A-2006-171729) proposes a driving method which realizes the low power consumption by arranging liquid crystal pixels connected to data lines in a LCD in a staggered manner such that the neighboring liquid crystal pixels are connected to different data lines and, at the same time, by dividing an output part of a driver LSI into an output part for first polarity and an output part for second polarity thus suppressing amplitude of a data line potential in the driver LSI to one half of amplitude of a corresponding data line potential in conventional dot inversion driving.
The related art can suppress the amplitude of the data line potential in the driver LSI. However, voltages of both polarities having first polarity and second polarity are applied to the data lines in the LCD and hence, a driver LSI output part is required to possess a high withstand voltage compared to conventional common inversion driving whereby there arise drawbacks such as the increase of a cost of the driver LSI or the increase of a circuit area and power consumption. In this manner, when the dot inversion driving is adopted for enhancing image quality of the LCD, there arises a drawback such as the increase of the cost or the increase of a circuit area to ensure the high withstand voltage of the driver LSI.